@Jaxblack Good question but it seems that if you don't open your Wallet for 2 Months then you get 2 Months Interest, which was not what I was expecting.

If you look at RL11 above you will see that there were 81 Days before the last payment. The simple Interest calculation gives 13% but correcting for / Month again gives 4.93% (Interest was 10% at that time)